The lack of humanitarian access granted by Myanmar's government to Rakhine state, where more than half a million Rohingya Muslims have fled violence, is "unacceptable", the U.N. said Friday.

"The access we have in northern Rakhine state is unacceptable", the head of the United Nations humanitarian office, Mark Lowcock, told reporters in Geneva.

A small U.N. team visited the crisis-wracked region in majority Buddhist Myanmar in recent days and described witnessing "unimaginable" suffering.

Myanmar has tightly controlled access to the state since last month when attacks by Rohingya militants prompted an army kickback that has sent 515,000 Rohingya fleeing to Bangladesh. Scores of Rohingya villages have been torched.

Lowcock said he believed "a high level" U.N. team would be able to visit the area "in the next few days." He repeated the U.N.'s call for the government to allow "unhindered [and] unfettered" access.

"Half a million people do not pick up sticks and flee their country on a whim," Lowcock added, stressing that the scale of the exodus was evidence of a severe crisis in northern Rakhine.

Turkey has been at the forefront of providing aid to Rohingya refugees, and President Recep Tayyip Erdogan has raised the issue at the U.N.

The U.N. has "substantial capacity" in Myanmar which can be quickly deployed to northern Rakhine once clearance is granted he added. A Myanmar official tally says hundreds of people died as violence consumed remote communities, including Rohingya. Hindus and ethnic Rakhine were also among the dead, allegedly killed by Rohingya militants.

Rights groups say the real death toll is likely to be much higher, especially among the Rohingya, while the U.N. has labelled army operations as "ethnic cleansing" against the Muslim group.

As many as 100,000 Muslim Rohingyas may have amassed near Myanmar's border to join the 515,000 refugees who have already fled to Bangladesh, the International Organization for Migration (IOM) said Friday in Geneva. Some 2,000 new arrivals per day are currently being recorded in the Bangladeshi coastal town of Cox's Bazar, said Joel Millman, the spokesman of the UN organization. The thousands of potential new refugees are waiting to cross the border from Buthidaung, a township in Myanmar's restive Rakhine state, he said, citing observers in the area.

The Rohingya, described by the U.N. as the world's most persecuted people, have faced heightened fears of attack since dozens were killed in 2012. Violence erupted in Myanmar's Rakhine state on Aug. 25 when the country's security forces launched an operation against the Rohingya Muslim community. It triggered a fresh influx of refugees towards neighboring Bangladesh, though the country sealed off its border to refugees. The region has seen simmering tension between its Buddhist and Muslim populations since communal violence broke out in 2012.